What is the difference between UUID v4 and v7?

UUID v4 is fully random (122 random bits) with no time component — best for general-purpose unique IDs where insertion order does not matter. UUID v7 embeds the current Unix timestamp in milliseconds in the first 48 bits, making IDs naturally sortable by creation time — ideal for database primary keys.

Are generated UUIDs truly unique?

With 122 bits of randomness (v4), the probability of collision is astronomically low even across billions of generated IDs. For practical purposes they are guaranteed unique. UUID v7 adds a timestamp prefix which further reduces collision probability within the same millisecond.

What format options are available?

Hyphenated (8-4-4-4-12, the standard), no-hyphens (32 hex chars), braces ({uuid}), and URN prefix (urn:uuid:uuid). All four formats represent the same 128-bit value.

How many UUIDs can I generate at once?

Up to 10,000 per batch. Generating 10,000 UUIDs takes about 100ms in modern browsers. The output is paginated to keep the page responsive.

Can I download the output as CSV?

Yes. Click "Download CSV" to save a single-column CSV with one UUID per row, ready to import into databases, spreadsheets, or test fixtures.

Is UUID v7 a published standard?

Yes. UUID v7 was standardised in RFC 9562 (May 2024), replacing the earlier draft. It is now widely supported in ORMs and database libraries.

Can I use these UUIDs as database primary keys?

Yes. UUID v4 is commonly used with UUID primary key columns. UUID v7 is preferred for clustered indexes (MySQL, SQL Server) because its timestamp prefix reduces page splits on insert.

Does this tool use crypto.randomUUID()?

UUID v4 uses crypto.randomUUID() when available (all modern browsers), falling back to crypto.getRandomValues(). UUID v7 is implemented from scratch using crypto.getRandomValues() with the RFC 9562 bit layout.

Generators /

UUID batch generator

Generate hundreds of UUID v4 or v7 at once. Choose your format, copy, or download as CSV for database seeding and test fixtures.

100% in your browser. UUIDs generated locally, nothing sent.

バージョン

数量

フォーマット

Output

How to use

Choose UUID v4 for random IDs or UUID v7 for time-ordered IDs.
Set the count — up to 10,000 per batch.
Pick a format: hyphenated is the standard; no-hyphens fits some database columns.
Click Generate, then Copy all or CSV to export.

Common use cases

Database seeding — generate primary key values for test tables.
Test fixtures — embed UUIDs in JSON or SQL fixtures for unit tests.
API mock data — paste UUIDs into Postman collections or mock servers.
Distributed systems — generate client-side IDs before network round-trips.

Also see: Random String Generator for custom token formats, Fake Name Generator for full user test records.

よくある質問

What is the difference between UUID v4 and v7?: UUID v4 is fully random (122 random bits) with no time component — best for general-purpose unique IDs where insertion order does not matter. UUID v7 embeds the current Unix timestamp in milliseconds in the first 48 bits, making IDs naturally sortable by creation time — ideal for database primary keys.
Are generated UUIDs truly unique?: With 122 bits of randomness (v4), the probability of collision is astronomically low even across billions of generated IDs. For practical purposes they are guaranteed unique. UUID v7 adds a timestamp prefix which further reduces collision probability within the same millisecond.
What format options are available?: Hyphenated (8-4-4-4-12, the standard), no-hyphens (32 hex chars), braces ({uuid}), and URN prefix (urn:uuid:uuid). All four formats represent the same 128-bit value.
How many UUIDs can I generate at once?: Up to 10,000 per batch. Generating 10,000 UUIDs takes about 100ms in modern browsers. The output is paginated to keep the page responsive.
Can I download the output as CSV?: Yes. Click "Download CSV" to save a single-column CSV with one UUID per row, ready to import into databases, spreadsheets, or test fixtures.
Is UUID v7 a published standard?: Yes. UUID v7 was standardised in RFC 9562 (May 2024), replacing the earlier draft. It is now widely supported in ORMs and database libraries.
Can I use these UUIDs as database primary keys?: Yes. UUID v4 is commonly used with UUID primary key columns. UUID v7 is preferred for clustered indexes (MySQL, SQL Server) because its timestamp prefix reduces page splits on insert.
Does this tool use crypto.randomUUID()?: UUID v4 uses crypto.randomUUID() when available (all modern browsers), falling back to crypto.getRandomValues(). UUID v7 is implemented from scratch using crypto.getRandomValues() with the RFC 9562 bit layout.

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